The present invention relates to a tachograph comprising a ciboid housing and a printing device. The printing device includes a thermal print head and a support which can be removed from the front side of the housing of the tachograph. Once removed it is possibile to reload a reel of paper or paper strip which forms the store of printing material. In addition, it is possible to reload a transport roll which, at least during printing, is operatively connected by a force fit to the thermal print head with the interposition of the printing material and is driven by a movement mechanism. The thermal print head is arranged in the housing of the tachograph and the transport roll and the movement mechanism are arranged in the support.
Tachographs which are not equipped for the use of circular graph charts as recording substrates but contain appropriately designed mass memories for the storage of the journey and working time data require printing devices which are suitable for documentation in the form of a visually legible record. The printing devices have to be arranged inside the tachograph since, in a driver""s cab of a utility vehicle there is generally no free space for the installation of an independent printer in communication with the tachograph.
An advantage of electronic tachographs includes the flexibility of mounting location within the driver""s cab. This advantage suffers when a printer is included with the electronic tachograph. Printers include certain requirements which limit tachograph location including the store of printing material and the necessity that the printing device be loaded with the store of printing material and for the starting section of the printing material to be brought into the printing position. This disadvantage is further exacerbated by the general design of tachographs themselves including a flat front face flush against a cab wall. Accordingly, only front loading of printer material is possible. To facilitate loading, it is necessary to use a support which can be displaced or pivoted out or folded out on the front side.
The structural concept mentioned in the beginning and described in German utility model DE-U 299 20 901.6 has the advantage of more beneficial utilization: of space than would be possible in the case of using commercially available printing units. In addition, in this design, threading the start of the paper strip between thermal print head and transport roll, and also precautions for eliminating a paper jam are dispensed with. Furthermore, the thermal print head can be fitted in a fixed location within the housing of the tachograph, so that even when the support is removed from the tachograph, immediate contact with dirt and moisture is largely avoided.
However, this assignment of the thermal print head to the housing causes problems inasmuch as the side walls and the top panel of the housing constitute relatively thin sheet metal parts. The installation space, for example, provided in a dashboard of a utility vehicle and corresponding to the format of the housing, does not permit any, outwardly projecting fixing elements. Further, reaction-free support of the spring-mounted thermal print head is necessary and seams and openings are to be avoided because of the intended tightness of the device. On the other hand, extremely little space is available for fitting the thermal print head in the direction of the vertical axis of the tachograph, and conditions of large-scale mass production have to be considered. This means that the fitting of the thermal print head is to be possible with the lowest possible expenditure on production and mounting and is to be easily reproducible with satisfactory functioning.
The above disadvantages are addressed by the present invention which includes providing a stable arrangement of a thermal print head within the housing of a tachograph which is suitable for the aforementioned conditions, takes up little space, can be implemented with components which are as simple as possible, and can be mounted in a straightforward manner.
The invention provides for a support bridge which can be pivoted counter to the action of at least one spring. The support bridge is provided to support the thermal print head and is fixed to a top panel of the housing of the tachograph.
An exemplary embodiment is characterized in that a retainer that is fixed to the top panel is provided for fitting the support bridge to the top panel.
The exemplary embodiment is distinguished in particular by the fact that the retainer is plate-like, that lugs provided with through holes are formed on the legs of the support bridge, and in that platforms assigned to the lugs and prepared for screw connections are integrally molded on the retainer.
The retainer and the top panel are connected to each other seamlessly at a plurality of points by using a sheet metal forming technique. In addition, the retainer has a cutout corresponding to the support bridge. Likewise, the support bridge is fixed to the retainer in such a way that the support bridge engages in the cutout in the retainer. Further, the legs of the support bridge point away from the top panel.
An advantage of the present invention includes the thermal print head being be arranged exclusively on the top panel of the housing and thus, since no longitudinal or transverse beams for fitting the thermal print head are required within the housing, there is optimum utilization of the overall space provided. The present invention also permits secure and stable fixing of the thermal print head. In particular, the support fixing o f the thermal print head not only has to support the contact force on the transport roll but, when the support is displaced, also has to absorb force components oriented transversely with respect to the direction of action of the contact force. The support bridge serves as a mount, within the retainer, in such a way that the support bridge is fixed and braced by the top part of the housing thereby being locked in the direction of movement of the support. In addition, it should be emphasized that, because of the retainer being fixed over the largest possible area to the top part of the housing, the invention effects reinforcement which is expedient for the fitting of the thermal print head, and that the thermal print head can be replaced in a straightforward manner.
A method applied to fixing the retainer to the top part, which has been developed by Tox Pressotechnik GmbH and Co. KG, Weingarten, and is known as the Tox circular point sheet metal connecting method, provides a seamless connection in the manner of a press fastener by means of material forming. This connecting technique satisfies the requirement for tightness and flatness of the top part of its outer side.
The present invention comprises a tachograph, comprising: a housing comprising walls defining at least an internal cavity and a top panel, a printing device located within said cavity and comprising a thermal print head and printing material, a transport roll located within said cavity and functionally associated via a force fit to said head such that said printing material is positioned between said transport roll and said head, said transport roll driven by a movement mechanism, a support located within said cavity for supporting said printing device, printing material, transport roll and movement mechanism, said support comprising means for extending said printing device out of said housing, and a support bridge for supporting said thermal print head, said support bridge being pivotably responsive to a spring action, fixed to said top panel.